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Re: n bits on of m bits

Cross-posted to 3 groups.

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Daniel Pitts wrote:
) On 12/19/11 2:44 PM, kym@kymhorsell.com wrote:
)> In sci.math The Last Danish Pastry<clivet@gmail.com>  wrote:
)> ....
)>>   public static int CountBinaryOnes(long x)
)>>   {
)>>     int result = 0;
)>>
)>>     while (x>  0)
)>>     {
)>>       ++result;
)>>       x&= x-1;
)>
)> The traditional method on 2s compl machinery is
)> 	x&= -x;
)>
)
) I've seen cleverer ways that are O(logn) best/worse case.

None of which is relevant to the OP because he wants to enumerate all
n-bit numbers that have exactly m bits set, and that can be done in
O(Choose(m,n)) time, instead of the O(2^n*logn) that this would do.

Hell, even if you just enumerated over all 2^n numbers you could still
keep/update a parallel count in O(1) time per step.


SaSW, Willem
-- 
Disclaimer: I am in no way responsible for any of the statements
            made in the above text. For all I know I might be
            drugged or something..
            No I'm not paranoid. You all think I'm paranoid, don't you !
#EOT

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n bits on of m bits Andrew Tomazos <andrew@tomazos.com> - 2011-12-17 08:05 -0800
  Re: n bits on of m bits Robert Wessel <robertwessel2@yahoo.com> - 2011-12-17 10:44 -0600
  Re: n bits on of m bits Dave <dave_and_darla@Juno.com> - 2011-12-17 08:56 -0800
  Re: n bits on of m bits richard@cogsci.ed.ac.uk (Richard Tobin) - 2011-12-17 17:22 +0000
  Re: n bits on of m bits "BartC" <bc@freeuk.com> - 2011-12-17 18:23 +0000
    Re: n bits on of m bits Andrew Tomazos <andrew@tomazos.com> - 2011-12-17 11:05 -0800
  Re: n bits on of m bits Robert Wessel <robertwessel2@yahoo.com> - 2011-12-17 13:24 -0600
    Re: n bits on of m bits Robert Wessel <robertwessel2@yahoo.com> - 2011-12-17 13:47 -0600
  Re: n bits on of m bits blp@cs.stanford.edu (Ben Pfaff) - 2011-12-17 11:28 -0800
  Re: n bits on of m bits "The Last Danish Pastry" <clivet@gmail.com> - 2011-12-19 21:52 +0000
    Re: n bits on of m bits kym@kymhorsell.com - 2011-12-19 22:44 +0000
      Re: n bits on of m bits Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2011-12-19 15:33 -0800
        Re: n bits on of m bits kym@kymhorsell.com - 2011-12-20 03:51 +0000
        Re: n bits on of m bits Willem <willem@toad.stack.nl> - 2011-12-20 10:05 +0000
          Re: n bits on of m bits Patricia Shanahan <pats@acm.org> - 2011-12-20 07:16 -0800
            Re: n bits on of m bits Dave <dave_and_darla@Juno.com> - 2011-12-20 07:29 -0800
              Re: n bits on of m bits Willem <willem@toad.stack.nl> - 2011-12-20 16:00 +0000
      Re: n bits on of m bits The Last Danish Pastry <clivet@gmail.com> - 2011-12-19 16:41 -0800
        Re: n bits on of m bits kym@kymhorsell.com - 2011-12-20 04:29 +0000
  Re: n bits on of m bits kym@kymhorsell.com - 2011-12-20 19:04 +0000
  Re: n bits on of m bits Robin Vowels <robin.vowels@gmail.com> - 2011-12-22 07:25 -0800
    Re: n bits on of m bits Willem <willem@toad.stack.nl> - 2011-12-22 15:58 +0000
      Re: n bits on of m bits Robin Vowels <robin.vowels@gmail.com> - 2011-12-22 16:26 -0800
        Re: n bits on of m bits Willem <willem@toad.stack.nl> - 2011-12-23 18:58 +0000
          Re: n bits on of m bits Robin Vowels <robin.vowels@gmail.com> - 2011-12-25 04:01 -0800
            Re: n bits on of m bits Dave <dave_and_darla@Juno.com> - 2011-12-25 09:22 -0800
  Re: n bits on of m bits Dr J R Stockton <reply1151@merlyn.demon.co.uk> - 2011-12-24 23:36 +0000
  Re: n bits on of m bits "io_x" <a@b.c.invalid> - 2011-12-31 16:32 +0100

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